Quantification of valproic acid in dried blood spots.

BACKGROUND: Therapeutic drug monitoring (TDM) of the antiepileptic drug valproic acid (VPA) is recommended in patients with multiple drug therapy or with concomitant disabilities to ensure treatment efficacy and avoid adverse reactions in both adults and children. The use of sampling techniques compatible with home sampling, such as dried blood spot sampling could potentially facilitate this for patients. AIM. To assess the usefulness of a bioanalytical method for quantification of VPA in dried blood spots. MATERIALS AND METHODS: Quantification was based on liquid chromatography-mass spectrometry (LC-MS), both for the DBS method and the plasma-based reference method. RESULTS: The method was validated in the range 10-1200 µmol/L. Total imprecision ranged from 4.9-8.9 (%CV) and accuracy was within ± 14%. CONCLUSION: The validated method has potential for evaluation in therapeutic drug monitoring in combination with home sampling of DBS. The impact of spot size can be controlled through acceptance criteria and hematocrit in the range 30-60% can be accepted in sampling. Comparison of VPA levels between plasma and whole blood cannot be done without considering the blood-plasma ratio.

Comparable lumefantrine oral bioavailability when co-administered with oil-fortified maize porridge or milk in healthy volunteers.

Co-administration of artemether-lumefantrine with milk is recommended to improve lumefantrine (L) absorption but milk may not be available in resource-limited settings. This study explored the effects of cheap local food in Uganda on oral bioavailability of lumefantrine relative to milk. In an open-label, four-period crossover study, 13 healthy adult volunteers were randomized to receive a single oral dose of artemether-lumefantrine (80 mg artemether/480 mg lumefantrine) with water, milk, maize porridge or maize porridge with oil on separate occasions. Plasma lumefantrine was assayed using high-performance liquid chromatography with ultraviolet detection. Pharmacokinetic exposure parameters were determined by non-compartmental methods using WinNonlin. Peak concentrations (Cmax ) and area under concentration-time curve restricted to 48 hr after single dosing (AUC(0-48) ) were selected for relative bioavailability evaluations using confidence interval approach for average bioequivalence. Lumefantrine exposure was comparable in milk and maize porridge plus oil study groups. When artemether-lumefantrine was administered with maize porridge plus oil, average bioequivalence ranges (means ratios 90% CI, 0.84-1.88 and 0.85-1.69 for Cmax and AUC(0-48) , respectively) were within and exceeded acceptance ranges relative to milk (90% CI, 0.80-1.25). Both fasted and maize porridge groups demonstrated similarly much lower ranges of lumefantrine exposures (bioinequivalence) relative to milk. If milk is not available, it is thus possible to recommend fortification of carbohydrate-rich food with little fat (maize porridge plus vegetable oil) to achieve similarly optimal absorption of lumefantrine after artemether-lumefantrine administration.

Adherence to artemether/lumefantrine treatment in children under real-life situations in rural Tanzania.

A follow-up study was conducted to determine the magnitude of and factors related to adherence to artemether/lumefantrine (ALu) treatment in rural settings in Tanzania. Children in five villages of Kilosa District treated at health facilities were followed-up at their homes on Day 7 after the first dose of ALu. For those found to be positive using a rapid diagnostic test for malaria and treated with ALu, their caretakers were interviewed on drug administration habits. In addition, capillary blood samples were collected on Day 7 to determine lumefantrine concentrations. The majority of children (392/444; 88.3%) were reported to have received all doses, in time. Non-adherence was due to untimeliness rather than missing doses and was highest for the last two doses. No significant difference was found between blood lumefantrine concentrations among adherent (median 286 nmol/l) and non-adherent [median 261 nmol/l; range 25 nmol/l (limit of quantification) to 9318 nmol/l]. Children from less poor households were more likely to adhere to therapy than the poor [odds ratio (OR)=2.45, 95% CI 1.35-4.45; adjusted OR=2.23, 95% CI 1.20-4.13]. The high reported rate of adherence to ALu in rural areas is encouraging and needs to be preserved to reduce the risk of emergence of resistant strains. The age-based dosage schedule and lack of adherence to ALu treatment guidelines by health facility staff may explain both the huge variability in observed lumefantrine concentrations and the lack of difference in concentrations between the two groups.

Field-adapted sampling of whole blood to determine the levels of amodiaquine and its metabolite in children with uncomplicated malaria treated with amodiaquine plus artesunate combination.

BACKGROUND: Artemisinin combination therapy (ACT) has been widely adopted as first-line treatment for uncomplicated falciparum malaria. In Uganda, amodiaquine plus artesunate (AQ+AS), is the alternative first-line regimen to Coartem(R) (artemether + lumefantrine) for the treatment of uncomplicated falciparum malaria. Currently, there are few field-adapted analytical techniques for monitoring amodiaquine utilization in patients. This study evaluates the field applicability of a new method to determine amodiaquine and its metabolite concentrations in whole blood dried on filter paper. METHODS: Twelve patients aged between 1.5 to 8 years with uncomplicated malaria received three standard oral doses of AQ+AS. Filter paper blood samples were collected before drug intake and at six different time points over 28 days period. A new field-adapted sampling procedure and liquid chromatographic method was used for quantitative determination of amodiaquine and its metabolite in whole blood. RESULTS: The sampling procedure was successively applied in the field. Amodiaquine could be quantified for at least three days and the metabolite up to 28 days. All parasites in all the 12 patients cleared within the first three days of treatment and no adverse drug effects were observed. CONCLUSION: The methodology is suitable for field studies. The possibility to determine the concentration of the active metabolite of amodiaquine up to 28 days suggested that the method is sensitive enough to monitor amodiaquine utilization in patients. Amodiaquine plus artesunate seems effective for treatment of falciparum malaria.

Amodiaquine, its desethylated metabolite, or both, inhibit the metabolism of debrisoquine (CYP2D6) and losartan (CYP2C9) in vivo.

OBJECTIVE: To study the extent of in vivo inhibition by the antimalarial drug amodiaquine, its active metabolite N-desethylamodiaquine, or both, of the metabolism of four probe drugs of the enzymes CYP2D6, CYP2C19, CYP2C9 and CYP1A2. METHODS: Twelve healthy Swedish volunteers received a cocktail of four probe drugs (debrisoquine, omeprazole, losartan and caffeine) to determine their baseline metabolic capacities. After a washout period, they received a 600 mg oral dose of amodiaquine hydrochloride; and 2-3 h later the cocktail was administered again. One week after the intake of amodiaquine, the subjects received the cocktail a third time. The levels of probe drugs and their metabolites as well as amodiaquine and its metabolite were determined by HPLC. RESULTS: Plasma levels of amodiaquine and N-desethylamodiaquine could be followed in all subjects for 6 h and 28 days, respectively. Among the 12 subjects, a 3-fold variation in amodiaquine AUC and a 2-fold variation in N-desethylamodiaquine AUC, were observed. The CYP2D6 and CYP2C9 activities of the subjects were measured by debrisoquine and losartan phenotyping tests, respectively. There were significant mean increases in debrisoquine metabolic ratio (MR) between baseline and the second cocktail [MR(2 h)-MR(baseline) 1.426 (95% confidence interval 1.159, 1.755), P=0.002; ANOVA, Fisher LSD test] and in mean losartan MR between baseline and the second cocktail [MR(2 h)-MR(baseline) 1.724 (95% confidence interval 1.076, 2.762), P=0.026; ANOVA, Fisher LSD test]. The effects on CYP2D6 and CYP2C9 activities subsided within a week after intake of amodiaquine as tested by the phenotyping cocktail. The changes in omeprazole MRs and caffeine MRs were not statistically significant between any of the study phases. CONCLUSION: A single dose of amodiaquine decreased CYP2D6 and CYP2C9 activities significantly compared to baseline values. Amodiaquine has the potential to cause drug-drug interactions and should be further investigated in malarial patients treated with drug combinations containing amodiaquine.